a) Field of the Invention
The present invention relates to a valve driving device which is used in a refrigerator compressor. Specifically, it relates to the open-close operational modes of a three-way valve.
b) Description of the Related Art
Conventionally adapted as a valve driving device, which is to be applied in a motor-driven refrigerant control three-way valve for a refrigerator, are a resin type or a ball type. FIG. 5 illustrates a cross-section of a portion of the configuration of a resin-type three-way valve 100, and FIG. 6 illustrates plan views of four open-close positions of the three-way valve 100 along the VI—VI line in FIG. 5. The three-way valve 100 can be operated in four modes: open-close mode, close-close mode, close-open mode, and open-open mode. The valve 100 is placed co-axially right under a stepping motor which is indicated by code 120. A rotor 122 is driven though a pulse control by a stator 121 and formed integral with a rotary shaft 101. A resin valve element 102 that rotates together with the rotary shaft 101 is connected to a bottom end of the rotary shaft 101 to freely move co-axially in the axial direction. The valve element 102 moves as a rib 103 protruded on the bottom surface of the valve element is pressed onto a valve seat 105 by the force of a compression spring 104.
The valve seat 105 has communicating holes 107a and 107b, which open inside a valve chamber 109 and are connected with two pipes 106a and 106b. The communication holes 107a and 107b are selectively communicated through an inlet 110 by the valve element 102 inside the valve chamber 109. The rib 103 is shaped to surround a recess portion 111 which is formed like a half-moon, as illustrated in FIG. 6, so that, according to the rotational angle of the rotary shaft 101, a single valve element 102 can control the separation of the communication holes 107a and 107b so as to switch one operational mode to another among the four modes. In other words, when either one or both of the communication holes 107a and 107b, which are provided at two adjacent positions, are surrounded by the half-moon-shaped recess portion 111, the communication of the holes with the inlet hole 110 is disconnected (closed) and the four open-close operational modes as illustrated in FIG. 6 can be obtained according to the rotational angle of the rotary shaft 101 with respect to the two communication holes 107a and 107b. 
FIG. 6(a) shows that the communication hole 107a is closed and the hole 107b is open; FIG. 6(b) shows that the holes 107a and 107b are both closed; FIG. 6(c) shows that the hole 107a is open and the hole 107b is closed; and FIG. 6(d) shows that the hole 107a and 107b are both open. In the above manner, the valve element 102 is arranged on the same axis as that of the motor rotary shaft 101 so that the valve element is rotated under pressure onto the valve seat 105 at the same speed as the rotary shaft 101 to change the four operational modes with the two communication holes 107a and 107b. 
FIG. 7 shows three usual operational modes of a ball-valve-type three-way valve 200. FIG. 7(a) shows openings 204a and 204b in a close-close mode in which both balls 206a and 206b are pressed onto a valve seat (not illustrated) with a protruded surface 210a, which is hatched, of a second cam 210. At that time, a first edge 212a of a control member 212 protruded on the outer circumference comes into contact with a first side edge 213a of a stopper 213 fixed in the valve chamber to determine a mechanical original position which is to be aligned with a driving pulse original position of the rotor 208a. In the second cam 210, the protruded surface 210a and the recessed surface 210b are gently connected by a slope 210c. 
When the rotor 208a is rotated counterclockwise by 90° (see an arrow) from the mode wherein the opening 204a is closed and the opening 204b is closed as illustrated in FIG. 7(a), the ball-type three-way valve 200 becomes the operational mode wherein the opening 204a is closed and the opening 204b is open as illustrated in FIG. 7(b). As the rotor 208a is further rotated by 180°, the valve 200 becomes the operational mode wherein the opening 204a is open and the opening 204b is closed.
When a second edge 212b of the control member 212 reaches the position to make contact with a second side edge 213b of the stopper 213, the rotor can be rotated no further in that direction. With the open-close operational mode configuration of the ball-type three-way valve 200 with the outlet pipes (not illustrated), the valve 200 always passes the close-close mode (see FIG. 7(c)) when the mode is changed from the close-open mode (FIG. 7(b)) to the open-close mode (FIG. 7(d)).